A shift register memory has a possibility that memory elements can be arranged with high density, so that the memory capacity can be significantly increased. To prevent structures of the memory elements from being complicated, it is undesirable to provide a control electrode for each bit (each digit) in the shift register memory. Therefore, it is necessary to perform a shift operation of a desired number of digits by adding a common action to all bit strings. However, it is not easy to shift all bit data without any error by such action.
As an example of the shift register, a charge coupled device (CCD) is widely known. Although the CCD was once expected to be applied to a memory, it is difficult to actually apply the CCD to a memory from a viewpoint of scaling-down and process cost because an electrode needs to be formed for each digit.